ArcGIS Server Basic Configurations

In case you’ve found ArcGIS Server configuration options confusing, here is a diagram of some basic configurations for an entry level ArcGIS Server setup. Any questions or comments ? Please Contact Us for more info.

Equipment Donation to RUA

The Royal University of Agriculture’s department of Land Management and Land Administration, were the recipients of 3 complete sets of GNSS survey equipment, donated by Trimble and Aruna Technology. The equipment will allow the extension of teaching to include current GNSS survey techniques, in addition to the optical survey techniques currently taught at the department. Present at the hand over ceremony, pictured below are Paul Gager, Technical Director at Aruna Technology, Vung Setha , Dean of the department of Land Management and Land Administration and a class of enthusiastic students studying at the undergraduate level.

Kamchay Hydropower Project – May 2012

This image shows the extent of the reservoir of the recently completed Kamchay hydropower project. The image is from the dry season 2012 (May) so the reservoir is not yet at full capacity. Expected maximum water level is 175m, somewhere between the 160 and 180m contours shown in this map.Note that there are some inaccuracies in the contour data due to the limitations of the data (from 1:100,000 scale topographic maps).

Bokor Mountain Development

Topology 101 for ArcGIS 10

There still exists some confusion about how we can work with topology in ArcGIS since workstation ArcINFO was discontinued some years back. So as a quick refresher, here is how we can work with topology in ArcGIS.

In geodatabases, topology is the arrangement that defines how point, line, and polygon features share coincident geometry. For example, street centerlines and census blocks share common geometry, and adjacent soil polygons share their common boundaries.

The next step is to validate the topology, which checks all features to see if they meet the topology rules. You can validate topology in ArcMap (while editing) or in ArcCatalog.ជំហានបន្ទាប់គឺការវាយតម្លៃរបស់ topology, ត្រួតពិនិត្យរាល់ features ថាតើគោរពទៅតាមច្បាប់របស់ topology ឬក៌អត់។ អ្នកអាចធ្វើការវាយតម្លៃ topology ក្នុងកម្មវិធី ArcMap (អំឡុងពេលដែលកំពុងប្រើប្រាស់វា) ឬ ArcCatalog ។

Correcting the errors can be done one by one in ArcMap using the error inspector. You can right-click the error in the list or on the map and click one of the available fixes. The fixes listed depend on the type of error.ធ្វើការកែរកំហុសអោយបានត្រឹមត្រូវម្តងមួយៗ នៅក្នុងកម្មវិធី ArcMap ដោយប្រើប្រាស់ឧបករណ៌ error inspector ។ អ្នកអាចចុច Mouse ខាងស្តាំ ទៅលើកន្លែងដែលមានកំហុសក្នុងតារាង ឬនៅលើផែនទី និងចុចមួយដងទៅលើឧបករណ៌ជួសជុល ។ ការជួសជុលអាស្រ័យទៅលើប្រភេទដែលមានកំហុស ។

Topology Example (c) ESRI

You can read more about creating and managing database topologies here;

Monthly Cloud Cover Data in Cambodia

These statistics are calculated from daily satellite observations and are useful for planning imagery acquisition.December to February are clearly the best months, but it is interesting to note that the late wet season (Nov) is better than April-May, though of course flood waters are still up in November.

SPOT6 Satellite – First Pictures

Three days after being orbited, SPOT 6 has delivered its first images

Astrium Services has posted the first images from the SPOT 6 satellite, just three days after its launch on 9 September.

SPOT 6 will assure continuity of data from the series of satellites operating since 1986, along with many technological innovations. Its unique responsiveness and acquisition capacity are set to benefit a broad spectrum of operational applications.

These first images present very varied landscapes, highlighting SPOT 6’s potential for applications like urban and natural resource mapping or agricultural and environmental monitoring. The wide imaging swath (60km), identical to that of the other SPOT satellites, makes SPOT 6 an ideal tool for covering vast territories, while its 1.5m resolution – against 2.5m on SPOT 5 – enables it to distinguish smaller features than ever before.

To post the images, all operational systems swung smoothly into action, from satellite tasking to image acquisition, reception and processing.

In January 2014, the arrival of SPOT 7 will bring more new services including daily revisits. Together, the SPOT 6 and SPOT 7 constellation will assure continued availability of high-resolution, wide-area products through to 2024.

Land Concession Monitoring – From Space

With the advent of newer earth imaging satellites with daily overpass and capture possibilities, it is now even easier to monitor land use change. For example, we can examine the history of development of two Economic Land Concessions (ELCs) inside the Beng Per Wildlife Sanctuary. The concessions were granted in early 2010 and by March 2011, land clearing was well advanced.

Clearing of Land Concessions as of March 2011

If we examine the historical imagery, we can see the incremental clearing that has occurred over 1 year.

SPOT vs. SRTM DEM Comparison

Well I’ve finally manged to get my hands on some SPOT DEM data for Cambodia for a project in the Southern Cardamoms. Quite an improvement over the SRTM (90m) data. The SPOT DEM has a resolution of 30m at the equator. From Astrium:

A SPOT DEM is a digital elevation model produced by automatic correlation of stereopairs acquired by the HRS instrument on SPOT 5.

Unlike a digital terrain model (DTM), which describes the distribution of terrain or “bare earth” heights, a DEM includes “first surface” elevations including vegetation and man-made structures.

SRTM DEM Detail. Scale approx 1:75,000

SPOT DEM Detail. Scale Approx. 1:75,000

For more info see http://www.astrium-geo.com/en/2790-elevation30-dem-spot-dem or please Contact Us

Dispelling Myths about Garmin GPS Accuracy

The declaration of the accuracy by Garmin GPS receivers often leads to confusion. What does it mean if the receiver states an accuracy of 4 m? This readout refers to the so-called 50 % CEP (Circular Error Probable). This means that 50 % of all measurements are within a radius of 4 m. On the other hand, 50 % of all measured positions are outside of this radius. Furthermore, 95 % of all measured positions are within a circle of twice this radius and 98.9 % of all positions are within a circle of 2.55 the radius. In the given example, nearly all positions are within circle with a radius of 10 m. The determined position is in the worst case accurate to 10 m.

Setting Up a Garmin GPS to Use Indian Datum

We often get asked about this question, so here are the full instructions on how this can be done:

Topographic maps in Cambodia use one of two datums; Indian 1954 and Indian 1960. By default, your Garmin GPS unit is set up to WGS84 datum, which is about 500m different to the Indian datums. If you want to display coordinates using one of the Indian datums, do the following;

In your unit, go to SETUP and then UNITS

Go to MAP DATUM and press the ENTER button

Garmin supports the ‘Indian Thailand’ datum which is close to, but not exactly the same as the other INDIAN datums. The differences are:

INDIAN 54 vs. INDIAN Thailand: 2.2 meters

INDIAN 60 vs. INDIAN Thailand: 6.4 meters

Remember that standard GPS is generally accurate to about 10m, so these differences may be insignificant to you. If you want to be more precise, you can select the USER datum and enter the following parameters.

INDIAN 1954

INDIAN 1960

DX

+ 217

DX

+ 198

DY

+ 823

DY

+ 881

DZ

+ 299

DZ

+ 317

DA

+ 861

DA

+ 861

DF

+ 0.28361370

DF

+ 0.28361370

In Cambodia, the old 1:50,000 scale topographic maps are based on the INDIAN 1960 datum. The newer 1:100,000 scale maps from the Reconnaissance Survey Project (the “JICA Maps”) from 1998-2002 are based on the INDIAN 1954 Datum.

Satellite Image of Kamchay Hydropower Project

This high resolution satellite image is of the Kamchay Hydropower in Kampot province Cambodia. The project is located inside Bokor National Park. The new road to the top of Bokor Mountain is visible in the bottom left hand corner. Kampot town is visible in the bottom right corner.

Aruna Technology are authorized distributors for satellite imagery from GeoEye, SPOT and RapidEye. Please Contact Us for more information.

River Bank Erosion Opposite Diamond Island

In case you’ve found ArcGIS Server configuration options confusing, here is a diagram of some basic configurations for an entry level ArcGIS Server setup. Any questions or comments ? Please Contact Us for more info.